For take off the flaps are set short to give extra lift,
on landing the flap are fully retracted and slow the Aircraft down by making the air flow downards,
The extra flap also gives extra lift at slow speeds,

The flaps, as well as slats (leading edge devices) act to increase the amount of lift the wing produces at a given airspeed by increasing the area and the camber, or curvature, of the wing. On approaches, this allows several things to happen. First, the aicraft can stay airborne at a much lower airspeed, which means the plane will take up less runway once it touches down. For example, the Beechjet 400A that Purdue owns can easily land at LAF (Purdue University Airport) with full flaps. Without flaps, however, the runway length required to slow down increases by over 100% and the aircraft must divert to an airport with longer runways. Also, because of the slower speed, flaps allow the aircraft to fly a steeper descent.

Adding to what Purdue said, the first 15 or so degrees of flaps add mainly lift while progressing beyond 15 or so adds more and more drag w.r.t. (with respect to) lift.

Also, there are different types of flaps:

Plain - simple hinged devices that move in a way similar to the elevators

Fowler - complicated devices that rotate down and slide aft. In the initial stages of extension, they mainly slide aft, adding to wing area and lift, further along in the extension progression they rotate down more and more.

Slotted - similar to plain flaps except there is an open slot between the flap and the wing when extended. This allows air to sneak through and holds the airflow more tightly to the wing. NOTE: Cessna high wing flaps are sometimes referred to as "slotted Fowler flaps" because they have similarities to both types

Split - surfaces that rotate down from the underside of the trailing edge of the wing.

Please forgive any typos or mistakes, while I was writing the post, there was an extremly irritating banner add that was flashing and I was getting quite ticked at it and posted as fast as possible . I must remember to write some hate mail to the company whose banner it was, now if only I could remember which company it was.........

To answer the question simply, the flaps do the same thing on landing as they do on take-off. They make the wing more curved so that it can still produce enough lift to keep the plane flying, while the plane's speed drops to a rate that can allow it to come into contact with the earth again, with safety.

Ralgha, what are you speaking of my good friend. There are no typos or mistakes in your aforementioned post. Nor do I see any banner, irritating or not, in any visual proximity to the body text area to cause such.
It's odd that someone would want to take blame for mistakes that weren't made and don't exist. But if you like that kind of stuff, and you're running low, I got some mistakes you could have. Big ones are $995 but that includes installation. Small ones I sell for $2.95 each, or you can get a package of 10 for $19.95 + shipping and handling. Please allow 6 to 8 weeks for delivery. No C.O.Ds.

Hmmmm...

Just a reminder to please spay or neuter your children.
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